This invention relates to dunnage bags for use in the shipment of freight and, more particularly, to weatherproof dunnage bags for use in the shipment of freight in open vehicles.
When transporting freight, it is customary to bridge the space between the freight and the walls of the freight carrying compartment to prevent the freight from shifting, which could result in damage to the freight and/or compartment. The benefits derived from preventing such damage must however be balanced against the cost of time, labor, and materials involved in installing spacing or bridging materials between the freight and compartment walls before shipment, of removing such materials after shipment, and of disposing of the removed spacing or bridging materials. To reduce the time and labor of installation and removal, inflatable dunnage bags have been used to prevent freight shifting. An inflatable bag is first inserted into the space between the freight and the compartment walls and is then inflated through a valve in the bag. Although inflatable dunnage bags have been made of rubber and canvas, because of the cost of such a bag, it is usually necessary to deflate and return it to the shipper for re-use. Thus, dunnage bags have most recently been made of a less costly material, such as paper, so that the bag can be disposed of after use. Generally a disposable dunnage bag has an airtight bladder made of polyethylene, rubber or a like expandable material enclosed within a plurality of folded bladder reinforcing paper sheets. The sheets are superimposed one over the other in their longitudinal or machine direction. Each sheet is folded flat along parallel fold lines so that its back and front walls are between the fold lines and one of its longitudinal edges overlaps its other longitudinal edge. Where the longitudinal edges of the sheet overlap, the overlapped edges are glued to form a seam extending in the longitudinal, machine direction of the sheet. Each outer sheet is folded and has its edges overlapped and glued after the preceding inner sheet has been folded, overlapped, and glued, so that when all of the sheets have been folded, overlapped and glued, the sheets are not connected to each other. When expanded, the sheets form a multi-ply tube with each sheet in contact with the immediately adjacent outer sheet so that the sheets reinforce each other.
The airtight bladder when inflated expands into contact with the innermost sheet and is supported by the multiply tube. A valve is attached to the bladder and extends through the sheets so that it is accessible for inflating the bag.
Prior to use of such a dunnage bag, the bag is flat. When it is desired to use the bag, it is positioned, for instance, between two pieces of freight in the freight carrying compartment and is inflated through the valve to maintain the pieces of freight in their initial position. When the freight reaches its destination, the bag is ripped open and rapidly deflates. The deflated bag can then be removed and disposed of.
The strength of the bag will of course depend upon the strength and quality of the sheets, which largely depends upon the conditions under which the freight is being transported. For instance, when freight is being transported in an open freight vehicle, weather conditions have an important effect on the strength of the sheets. It has been found that under rainy conditions moisture enters the dunnage bag to significantly affect the strength of the paper protecting the bladder, so that premature rupture of the bladder results.
Because it is not economical to return to using the more expensive, non-disposable type of dunnage bag, which may be less apt to prematurely rupture, then a substantially paper dunnage bag which is waterproof is necessary.
Attempts to provide an inexpensive, reliable, substantially paper dunnage bag have been made. For instance, a prior art dunnage bag is shown in FIGS. 1 and 2 of this invention. The bag has an air bladder 10 enclosed within a plurality of folded bladder reinforcing sheets, indicated generally at 11. Surrounding the outermost of the sheets is a moisture resistant material in the form of an outer bag 12. Bag 12 surrounds the dunnage bag to prevent moisture from pervading the bladder reinforcing sheets. However, it is readily appreciated that the cost of such an outer bag 12 having the same size as a dunnage bag used in rail-cars and trucks makes this type of weatherproof dunnage bag impractical. Essentially, it has now been found that only certain portions of a dunnage bag need be protected by a layer of moisture resistant material if the present invention is utilized. For instance, it has been found that only the portions of a dunnage bag having exposed seams, folds, or similar openings where moisture may enter the bag actually need to be protected from invasion by moisture with such a layer.
A second disadvantage of the prior art dunnage bag shown in FIGS. 1 and 2 is that outer bag 12 has not been found to be efficient in preventing moisture from entering the bag around the bladder inflating valve of the bag, generally indicated at 13. Note in FIGS. 1 and 2 that valve 13 is placed over and inserted through an opening defined by portions of bag 12 so as to be in communication with bladder 10. It should also be noted that this prior art dunnage bag includes various structures mounted on valve 13, such as a reinforcing layer of rubber 12a affixed to bag 12 around valve 13, a first clip 15, rubber washers 16, a handle 17, and a grommet 14. The portions of outer bag 12 defining the opening through which valve 13 extends are encased by grommet 14 and do not actually abut against valve 13. Thus, in this prior art bag, outer bag 12 does not provide a moisture tight seal with the valve, so that moisture is prevented from leaking into the bag around valve 13.
The present invention overcomes the above-mentioned disadvantages. The weatherproof dunnage bag of the present invention utilizes moisture resistant overslips to cover only the ends of a substantially paper dunnage bag. Thus, the overslips cover and weatherproof those areas of the bag particularly prone to moisture damage. The dunnage bag of the present invention also includes a moisture resistant tape covering the longitudinal seam in the outermost sheet of the bag between the opposite ends of the bag covered by the overslips. Further, the dunnage bag of the present invention includes a moisture resistant coating on the outermost sheet. Thus, the dunnage bag of the present invention is weatherproofed without the need for being totally enclosed by a second moisture resistant bag. To avoid leakage of moisture into the bag from around the area of the valve, in the dunnage bag of the present invention, the opening defined in the overslip covering the valve is smaller than the outer diameter of the valve so that the overslip itself fits tightly around the valve to prevent moisture from pervading the sheets of the bag.
An object of the present invention is to provide a weatherproof dunnage bag less expensive and more efficient than the dunnage bags known in the prior art.
Another object of the present invention is to provide a dunnage bag for use in an open freight transporting vehicle which can be used without sustaining substantial damage by moisture pervading the sheets of the bag.